This invention relates to improved means for contacting a container as it is slid across the top of a weight platform so as to maintain its position in indexed relation to other portions of the system. More particularly, in the system of U.S. Pat. No. 4,344,493 of Andrew R. Salmonsen, filed Mar. 6, 1981 and issued Aug. 17, 1982 there is described and claimed a high-speed weighing and conveying apparatus in which open-topped cans are filled at a filler station and moved slidingly in a train along a rail system and across a weigh platform to a closer. In such system it is required that the cans be filled, weighed and closure initiated at particular times with reference to the operations of the filler, weigher and closer, and in relation to the same operations for other cans in the train. This is accomplished in this example by means of an endless-chain arrangement which moves, below the level of the top of the weigh platform, from a position ahead of the weigh platform to a position downstream of the weigh platform, and which has on it a series of spaced-apart upstanding lugs each of which extends upwardly above the top of the weigh platform so as to contact the upstream edge of the bead at the bottom of each can and to maintain a guiding contact with the bead as the can slides over the weigh platform. During the time period in which the can is sliding over the platform, the can is intended to be substantially free with respect to its up and down motion, so that the corresponding up and down motion of the weigh platform properly represents the weight of the can and contents and an accurate weight indication is produced.
It has been found that this method of conveying the cans across the weigh platform has an adverse effect upon the accuracy of weighing after the apparatus has been used for an extended period of time. This has been found to be due to the fact that the can beads, which have a relatively small radius of curvature in radial planes and extend radially outward from the main body of the can, eventually tend to wear an indentation into the leading or contacting edges of the lugs. This indentation tends to support some of the can weight as the can moves across the weigh platform, thus resulting in some error in weight indication; in addition, this indentation tends to restrict vertical movement of the cans while they are are on the weigh platform, so that they do not move in exact natural vertical oscillation with the platform, due to the fact that the cans are to some extent seated in the indentations.
Such resultant errors in the indications of weight of container and contents require that the can be filled higher than necessary, in order to assure that the can will be adequately filled; if a more exact weight indication can be obtained, then the amount of product placed in the can can be restricted more exactly to the required minimum amount, and a considerable saving in the amount of product dispensed thereby realized over a substantial period of operation.
It is therefore an object of the invention to provide new and useful contacting means for contacting the upstream side of a container as it is slid over a weigh platform.
Another object is to provide such apparatus which permits the weight of the container to be fully supported by the weigh platform and to move freely up and down along with the weigh platform, even after very long periods of repetitious use of the contacting means.
A further object is to provide such an improved contacting means which results in more accurate weight indications.